Smash Up calls itself a “shufflebuilding” game. It consists of 20-card half-decks of factions like aliens, dinosaurs, pirates, and zombies; pick two, shuffle them together, and now your alien dinosaurs are squaring off against zombie pirates. It’s fun and I’ll probably review it later.
The base game comes with eight factions, and each expansion adds four. Each expansion can be played as a standalone two-player game, and any pair of them is a four-player game just like the original. Each of them is another set of options to add to any other set of options. Its modularity supports players in deciding what range of options they want to play with (and pay for).
That same modularity means there is value in duplicate sets. It does not help to have a second set of the same Dominion cards or another Settlers board unless you want to play two games at once. In Smash Up, you can combine the base set with itself or expansions with themselves so that your four corners might be alien dinosaurs, alien zombies, zombie pirates, and dinosaur pirates. Choices are exclusive only to the extent that cards are limited. Again: more potential options and, on the business side, more options players can usefully pay for.